Circulating immunoreactive growth hormone releasing hormone concentrations and growth hormone response to growth hormone releasing hormone in short children

Abstract

To study the role of peripheral immunoreactive growth hormone releasing hormone (ir-GHRH) concentrations and the GHRH test in the evaluation of growth hormone (GH) secretion in short stature, 46 children with a mean age of 9.4 years (range 1.6-16.3 years) and a mean relative height score of -3.2 SD (range -5.0-2.1 SD) were investigated. The children were divided into prepubertal (n = 35) and pubertal (n = 11) and the prepubertal children further into three groups based on their maximal GH responses to insulin-induced hypoglycaemia (IIH) and clonidine: (1) GH deficient subjects (maximal GH < 10 micrograms/l in both tests); (2) discordant responders (maximal GH < 10 micrograms/l in one test and > or = 10 micrograms/l in the other); and (3) normal responders (maximal GH > or = 10 micrograms/l in both tests). Peripheral ir-GHRH concentrations were measured during the IIH test by radioimmunoassay after purification of plasma samples on Sep-pak cartridges. Among the prepubertal children 10 fell into group 1, 16 into group 2 and 9 into group 3. Children in group 1 were older than those in group 3. There were no significant differences in relative heights and weights or absolute and relative growth velocities between the groups. Subjects in groups 1 and 2 had lower maximal GH responses to GHRH than those in group 3. There were no significant differences in the basal plasma ir-GHRH concentrations between the groups. Nine children (19.6%) had somatotrophs with a poor response to a single dose of exogenous GHRH (maximal GH < 10 micrograms/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Low-Dose Oral and Intravenous Dexamethasone Administration on Growth Hormone Secretion in Children

“…In contrast, all GH-deficient chil dren had significant GH elevations after GHRH adminis tration. although of variable magnitude, as reported pre viously in the literature [7,37,38]. As GHRH increases GH release by a direct pituitary action [39], our data con firm previous suggestions that the acute effect of dexa methasone is probably mediated by the hypothalamus [21,28], Inhibition of hypothalamic somatostatin release may have a role in this GH-stimulatory effect [9,24], A direct action of corticoids on somatostatinergic neurons has been suggested, which is apparently independent of cholinergic pathways [9,20,40], Although intravenous dexamethasone administration has advantages over the pharmacological tests employed routinely to evaluate GH deficiency, the length of time to perform the test is a major drawback.…”